docs: def _function_lookup(name, module):
      """Searches the function between the registered ones.
      If not found, it imports the module forcing its registration.
  
      """
      try:
          return _registered_functions[name]
      except KeyError:  # force function registering
          __import__(module)
          mod = sys.modules[module]
          getattr(mod, name)
  
          return _registered_functions[name]